In the electronics industry, there is a constant demand for electronic devices, such as integrated circuits ("ICs") or semiconductor chips, to be produced less expensively and in smaller dimensions while simultaneously increasing the density of electronic functions within the devices. One way to increase productivity of such electronic devices, and thereby reduce their unit cost, is to increase the test speed of the devices by testing a plurality of them at the same time.
It has become a test technology standard to place a number of electronic devices to be tested on a test tray and position them so as to be engaged by a test head plate having a number of corresponding test contactors. One device is placed on a seat of a carrier module, and each carrier module is provided with one or more device seats. A number of modules are then positioned in both columns and rows on a test tray. The test tray having a number of carrier modules is arranged so as to be in vertical alignment (either above or below) with a test fixture. The test fixture includes test contactors (test pins) for contact with pins of each device to be tested for supplying and receiving the test signals from the device. Each module is aligned with a corresponding test contactor so that when either the test tray or the test fixture are moved in a vertical direction toward the other, the contactor engages the electronic device positioned within the carrier module.
The contactor is provided with a number of test pins or leads which come into electrical communication with the leads of the electronic devices to be tested. The automatic test handler is electrically connected to a electronic device test system, for example, an IC tester which includes a test signal generator for supplying a test signal to the device, and with a signal comparator for analyzing the results of the test. Based on such results, the electronic devices are transferred to another location in the test process and sorted for proper handling.
Thus, in order to increase the volume of electronic devices that can be tested in the manner described above during a given period of time, it is desirable to maximize the efficiency of the contact test assembly, including primarily the test contactor and the carrier containing the electronic devices. However, such standard electronic device test systems described above suffer from a number of disadvantages. First, it is difficult to accurately layout and position the device to be tested with respect to the contactors in the test fixture for engaging the electric leads of the devices. As a result, a problem arises in that an electrical contact between the leads of the device and the contactor is not perfect. It is especially true when an electronic device to be tested becomes small and a spacing between the leads of the device becomes small. Further, when a large number of electronic device to be tested are arranged on the test tray, the positioning error in one unit of the device will increase by the multiple of the number of the devices aligned on the tray and thus cause a serious misconnection problem.
Secondly, even if the large number of devices to be tested are aligned accurately on the test tray, the accuracy of positioning may be degraded because of a small deformation or curvature in the test tray caused by uneven thermal expansion or contraction from immersion in a temperature regulated test chamber. Such test chambers are commonly used to simulate particular device operating temperatures. In that situation, the distance from the contactor to the corresponding device to be tested may change and, as a result, the electrical connection for some devices will be imperfect due to the lack of sufficient proximity between the contactor leads and the device leads, while some other devices will mate with the contactor leads too tightly. Thus, there exists a problem with using large trays in order to increase the number of devices simultaneously tested in the test handler and, therefore, the number of electronic devices that can be tested at one time is currently limited.
Third, for improving the high frequency performance and increasing the device function density, the spacing between the leads of the recent electronic devices to be tested is getting smaller and smaller, and as a result, the leads are becoming thinner. At the same time, the length of the leads is getting shorter. In testing these smaller electronic devices in a test handler, it is sometimes difficult to firmly contact the leads of the devices with the contactor leads, since both leads are not physically strong enough to sustain the firm contact force between them, and are prone to breakage.
Additionally, the size and configuration of standard electronic chips are rapidly changing. Some of the high speed ICs have very short signal leads, instead of the relatively longer leads used in the conventional dual in-line-package ("DIP") type. For example, the newest type of IC device is molded in a package called a TSOP (Thin Small Outline Package), which will be described in more detail later. When utilizing a test tray to test such IC devices, it is necessary to employ a new carrier module to secure an electrical isolation between the leads and also to eliminate the deformation of the leads of the IC devices.
Thus, there s a serious need in the electronic device test industry for a contact assembly which can overcome the problems described above.